The invention is directed to a machine tool for the drilling and/or grinding treatment of workpieces, comprising at least two headstocks.
Machine tools are known wherein the headstock removes or resp. returns the tools directly from/into a fixed or movable tool magazine. In such machine tools, the headstock must be advanced to the tool magazine upon completion of a treatment process. At the tool magazine, the tools are exchanged, and the headstock is subsequently guided back to the workpiece. The exchanging of tools requires a considerable length of time, which is caused not only by the movement processes to be performed by the headstock but also by the time losses due to the decelerating and accelerating of the working spindle. Throughout the exchanging of tools, the machine tool is not available for treatment processes.
In machine tools comprising a large number of working spindles in a revolver configuration, the removing of one working spindle from the workpiece and the advancing of another working spindle to the workpiece along with the coupling and accelerating processes takes considerable time. Although, during operation of one working spindle, another working spindle can be equipped with new tools, this will require high expenditure in working spindles. Further, such an approach necessitates the use of a tool magazine which is advanced to the revolver system located in its operating position.
A machine tool forming basis of the preamble of claim 1 is known from JP 59-69242 A (Patent Abstracts of Japan M-317, Aug. 15, 1984, Vol. 8, No. 177). This machine tool is provided with a support whereon two headstocks are movable in vertical direction independently of each other. Each headstock has a dedicated tool magazine arranged thereabove which is moved together with the headstock. The transfer of the tools from a tool magazine to the appertaining headstock is performed by a swivel arm. The whole support of the machine tool is displaceable in feeding direction (towards the tool). This machine tool offers the advantage that a respective one of the headstocks can engage the workpiece while an exchange of tools can be carried out on another headstock. Thus, considerable time is saved because no time requirements exist for exchanging the tools.
Further, a machine tool known from Patent DD 263 725 A1 comprises a single headstock to be displaced vertically on the support. Additionally, the headstock can be moved horizontally in its longitudinal direction to allow exchange of tools using a tool magazine. The tool magazine is arranged before the machine support and carries various tools on a horizontally moveable slider, such that each tool can be moved into a transfer position for the headstock. The guiding path for the tool magazine must be at least twice as long as the magazine slider carrying the tools.